When should the aux fan kick-in?

[gvilkelis]

Hello,

I have just fixed the ballast resistor problem on my aux fan, and it is working fine when I turn A/C on.

But anyone knows at what temperature it should start blowing without A/C turned on?
My temperature gauge arrow was halfway between 1/2 and 3/4 marks, but the aux. fan was not blowing. Is this normal, or should I replace the aux. fan switch in radiator?

And is it normal, that in heavy traffic and hot weather the temperature gauge arrow stays halfway between 1/2 and 3/4 marks?

BTW, my car is 525, E34 M20 1988

thank you,
g.v.

[JonE]

On my 535i the aux fan was coming on "low" either with AC switched on or when temp guage was between 1/2 and 3/4, it came on "high" at or above 3/4. This was happening in traffic when my fan clutch was shot. When the car is hot and you have the hood up you should feel alot of air blowing from the engine fan if the fan clutch is good. If good, and you shut the hot car off the engine fan should come to an abrupt stop. Mine was "freewheeling" and not blowing alot of air. Replaced the fan clutch and no overheating problem thereafter. Check that fan clutch operation.

[western99]

If not, the something is not working properly. Also your temp guage should always be at 12 o'clock. Regardless.


Hello,

I have just fixed the ballast resistor problem on my aux fan, and it is working fine when I turn A/C on.

But anyone knows at what temperature it should start blowing without A/C turned on?
My temperature gauge arrow was halfway between 1/2 and 3/4 marks, but the aux. fan was not blowing. Is this normal, or should I replace the aux. fan switch in radiator?

And is it normal, that in heavy traffic and hot weather the temperature gauge arrow stays halfway between 1/2 and 3/4 marks?

BTW, my car is 525, E34 M20 1988

thank you,
g.v.

[winfred]

turn the key on and play with the wires on the switch on the side of the radiator with a jumper wire to check it's operation, the engine can be overheating it's ass off and not turn on the fan if the hot water is not getting to the switch from a stuck thermostat

[DanDombrowski]

A little clarification, as I'm trying to troubleshoot my aux fan also.

On the passenger side of the radiator, there is a sensor of some kind that plugs into the radiator, it has 3 wires. This is what you're talking about, right? I don't remember the colors, pretty sure one was brown. I tried jumpering all different ones, but got nothing. I didn't have my voltmeter or bentley with me so I didn't worry about it and just set it aside.

So in short, what do each of the three wires do, and which ones should you jumper? Does one of them need to be shorted to ground?

[gvilkelis]

Yes, it does start blowing when A/C is on.
About the cooling system - I previous owner has replaced radiator ar water pump, I have replaced fan clucth and the termostat.
What else could be wrong with the cooling system?
One strange thing I have notice - if I press accelerator pedal to 5000 rpm, then for about 1 second or less one hose squeezes, then it comes back to its normal shape. Does this indicates, that there is a circulation problem somewhere or is it normal?
How could I detect a circulation problem?

[gvilkelis]

Check the page at:
http://www.nmia.com/~dgnrg/page_20.htm

[gvilkelis]

My fan clutch has been replaced about half a year ago, I have also replaced the termostat, radiator and water pump were also replaced earlier.

I am running out of ideas what could be wrong with cooling system

[western99]

If not, I think that you may have a seized fan from what I have read in the previous postings.

[DanDombrowski]

perfect, thanks

[gvilkelis]

Yes, the aux fan does come on on low mode when AC is on, but I have read, that it should also start when coolant temperature reaches some predefined tempereture.

[Dan in NZ]

I went through the exact same thing a couple of weeks ago... My temp would sit at about 1/3rd of the way between 1/2 and 3/4. Under load the temp would go up to 3/4. My fan clutch was shot, so that was replaced, but still had the overheating problem. It turned out my radiator was about 75% blocked, the bmw dealer did 4.5 hours free labour to remove&re-install the radiator because the fan clutch didn't solve the problem, then I paid the radiator specialist NZD$100 to clean it out. The temp guage now sits at exactly 12 o'clock no matter what.

Also, even when the gauge was at 3/4, the aux fan never came on, but it always operates on low speed with the a/c on. Perhaps the thermo-switch fails but people never find out because these cars shouldn't get that hot if they are in good order?

[winfred]

with the clogged radiator the switch wasn't getting hot enough, seen it several times with the upper hose hotter then hell and the lower is cool to the touch and lots of pressure, when it's doing that the fan clutch is useless because the center of the radiator is usually cold and not warming the clutch to engauge it


Also, even when the gauge was at 3/4, the aux fan never came on, but it always operates on low speed with the a/c on. Perhaps the thermo-switch fails but people never find out because these cars shouldn't get that hot if they are in good order?